这与我之前的帖子“http://stackoverflow.com/questions/8788825/linux-udp-server-unreachable-from-window-7”有关，已经解决了。现在我转到将AVD连接到Linux服务器的原始工作。
我使用以下代码连接服务器
import java.net.*;
class UDPClient {
public final static int DesitnationPort = 9999;
private int mCounter;
private DatagramSocket mClientSocket;
private InetAddress mServerIPAddress;
private byte[] mDataBuffer;
private DatagramPacket mSendPacket;
private DatagramPacket mReceivePacket;
//Constructor
public UDPClient() {
//Time to make the private data good one
mCounter =1;
try {
mServerIPAddress = InetAddress.getByName("192.168.2.2");
}
catch(UnknownHostException e)
{
System.out.println("Host cannot be resolved :( ");
}
System.out.println("Host has been resolved The IP is valid one ");
try {
mClientSocket = new DatagramSocket();
}
catch(SocketException e)
{
System.out.println("Socket could not be created :( ==> " + e.getMessage());
}
System.out.println("Socket has been created ");
String temp = "This is from the Client == To my Dear Sever :) counter = " + mCounter;
mDataBuffer = temp.getBytes();
mSendPacket = new DatagramPacket(mDataBuffer, mDataBuffer.length, mServerIPAddress, DesitnationPort);
System.out.println("Datagram has been made now ");
System.out.println("Data ==>"+ mSendPacket.getData());
System.out.println("Data ==>"+ mSendPacket.getPort());
System.out.println("Data ==>"+ mSendPacket.getSocketAddress());
System.out.println("Data ==>"+ mSendPacket.getLength());
}
public void SendDataToServer(){
try {
if(!mClientSocket.isClosed()) {
String temp = "This is from the Client == To my Dear Sever :) counter = " + mCounter;
mDataBuffer = temp.getBytes();
mSendPacket = new DatagramPacket(mDataBuffer, mDataBuffer.length, mServerIPAddress, DesitnationPort);
mClientSocket.send(mSendPacket);
System.out.println("Send the packet");
mCounter++;
}
else {
System.out.println("Socket is closed");
}
}
catch(Exception e)
{
System.out.println("Could not send the data :( ==> " + e.getMessage());
}
}
public void ReceiveDataFromServer() {
byte[] tembuff = new byte[1024];
mReceivePacket = new DatagramPacket(tembuff, tembuff.length);
try {
if(!mClientSocket.isClosed()) {
mClientSocket.receive(mReceivePacket);
}
else {
System.out.println("Socket is closed");
}
}
catch(Exception e)
{
System.out.println("Could not Receive the data :( ");
return;
}
String data = new String(mReceivePacket.getData());
System.out.println(" Received the Data => " + data);
}
}
当我在java程序中使用这样的类时，这段代码很有效： -
class TryingWithClient {
public static void main(String a[]) {
UDPClient mClient = new UDPClient();
while(true) {
System.out.println("While Starting");
mClient.SendDataToServer();
mClient.ReceiveDataFromServer();
}
}
}
当我在AVD项目中使用相同的代码时，我会在以下行获得Null指针异常： -
public void SendDataToServer(){
try {
if(!mClientSocket.isClosed()){ //<==@ this call Null exception occurs
浏览互联网＆amp; android开发网站我得出结论，我错过了我添加到AVD的GMS / GPS功能。我仍然无法得到任何关于此的线索。
这是我调用上述UDPClient的代码。
public class StreamingProjectActivity extends Activity {
/** Called when the activity is first created. */
//All buttons
//private static final String LOG_TAG = "StreamingTest";
private StreamButton mStreamButton = null;
private UDPClient mClient= null;
class StreamButton extends Button {
boolean mStartStreaming = true;
OnClickListener clicker = new OnClickListener() {
public void onClick(View v) {
onStream(mStartStreaming);
if (mStartStreaming) {
setText("Stop Streaming");
} else {
setText("Start recording");
}
mStartStreaming = !mStartStreaming;
}
};
public StreamButton(Context ctx) {
super(ctx);
setText("Start Streaming");
setOnClickListener(clicker);
}
}//class StreamButton Ends
@Override
public void onCreate(Bundle icicle) {
try {
mClient = new UDPClient();
System.out.println("==========> Client created sucessfully :) <====== ");
super.onCreate(icicle);
LinearLayout ll = new LinearLayout(this);
mStreamButton = new StreamButton(this);
ll.addView(mStreamButton,
new LinearLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT,
0));
setContentView(ll);
System.out.println("Trying Step 2 now ");
}
catch(Exception e)
{
System.out.println("Activity could not be launched :( ");
}
}
//public StreamingTest()
public StreamingProjectActivity(){
System.out.println("Constructor ====>");
System.out.println("Constructor <====");
}//Constructor
private void onStream(boolean start) {
if (start)
{
mClient.SendDataToServer();
mClient.ReceiveDataFromServer();
try
{
Thread.sleep(4000);
}catch (InterruptedException ie)
{
System.out.println(ie.getMessage());
}
}
}//onStream
}
请帮助。
答案 0 :(得分：1)
好的，首先：永远不要使用System.out.println("some msg " + e.getMessage());打印捕获的异常请为此使用Log.e(TAG, "my message", e);。所以你实际上会看到一个堆栈跟踪。
第二：我打赌这段代码会抛出一个错误（检查你是否在LogCat输出中看到了打印）：
try {
mClientSocket = new DatagramSocket();
} catch(SocketException e) {
System.out.println("Socket could not be created :( ==> " + e.getMessage());
}
这是mClientSocket仍然可能为空的唯一原因。由于此调用可能出错，因此在检查套接字是否已关闭之前，应考虑检查null。
答案 1 :(得分：0)
我之前的解决方案中的问题是我正在混合使用GUI和网络操作在同一个线程中被称为“StricMode.ThreadPolicy”（虽然，我的问题只是行话中提到的部分）。
我得到了这些例外“android.os.NetworkOnMainThreadException＆amp; android.os.StrictMode $ AndroidBlockGuardPolicy.onNetwork（StrictMode.java:1099）”，我只有在应用了WarrenFaith的建议（感谢Warren）之后才能解决这个问题。 / p>
仅在违反“StricMode”时抛出这些内容。
解决方案：只需将UI工作与网络分开即可。我必须为此编写以下代码：
enum ClientThreadStates {
eUndefined,
eStopped,
eRunning,
eIdle,
eSendToServer,
eReadFromServer
}
public class ClientThread extends Thread {
private UDPClient mClient= null;
private ClientThreadStates mStateOfTheThread = ClientThreadStates.eUndefined;
private static String mLOG_TAG;
public ClientThread(String s){
mLOG_TAG = s;
mStateOfTheThread = ClientThreadStates.eStopped;
mClient = new UDPClient(s);
start();
}//constructor
public void SetState(ClientThreadStates paramState) {
mStateOfTheThread = paramState;
}
public ClientThreadStates GetState() {
return mStateOfTheThread;
}
private void Action(ClientThreadStates s) {
synchronized(s) {
switch(mStateOfTheThread) {
case eRunning: //fall
case eIdle: break;
case eSendToServer: mClient.SendDataToServer(); break;
case eReadFromServer: mClient.ReceiveDataFromServer(); break;
}
try {
mStateOfTheThread.wait();
}
catch( InterruptedException e ){
Log.e(mLOG_TAG, "Got Exception at wait <==", e);
}
}
}
public void run() {
mStateOfTheThread = ClientThreadStates.eRunning;
System.out.println("In Thread.run .. The State is " + mStateOfTheThread);
while(ClientThreadStates.eStopped.compareTo(mStateOfTheThread) < 0){ //state >stopped
Action(mStateOfTheThread);
}//while
}//run
}//class ClientThread
最后在状态上的两个线程上同步，如下所示：
private void onStream(boolean start) {
ClientThreadStates State = mClientThread.GetState();
synchronized(State) {
if (start) {
mClientThread.SetState(ClientThreadStates.eSendToServer);
}
else {
mClientThread.SetState(ClientThreadStates.eReadFromServer);
}
try {
State.notify();
}
catch( IllegalMonitorStateException e ) {
Log.e(LOG_TAG, "Got Exception @ notify <==", e);
}
}
}//onStream
}//StreamingProjectActivity
现在代码运行完美。
感谢。 Ashutosh说